DID YOU SEE THE GOOGLE ADSENSE ADS ON THE RIGHT?
1) MORE ON HYPOGENIC CAVES
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In the preceding post, I introduced you to hypogenic caves and we discussed Villa Luz, a cave with mixed hypogenic and surface features. Here we will look at a much more hypogenic cave which developed an ecosystem almost completely preserved from outside influence for about 500 millions years. The hypogenic cave I'll invent in "WE SHARE" will be a mix of Movile and Villa Luz but at a much deeper level (minus 600 meters) compatible with the geology of the area where I locate it and with my taste for vertical caving adventures..
2) MOVILE: AN ALMOST OXYGEN FREE ECOSYSTEM
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The Movile cave is situated in Romania near th
Movile is an active hypogenic cave, carved by sulphuric acid like Villa Luz. However, opposed to Villa Luz, it has been almost totally isolated from the surface since at least half a million years. The processes of rock carving by bacteria and establishment of an isolated ecosystem are thus much purer than in Villa Luz where surface and hypogenic features interfere strongly.
Movile is host to an endemic invertebrate fauna which is probably quite unique (it should be carefully compared to the one in Villa Luz but I do not know of any such comparison). It has adapted, like Villa Luz but much more completely, to the lack of light and oxygen and feeds on the bacteria which themselves feed on minerals dissolved in the water.
The Movile ecosystem is thus autarcic, without any input of solar energy (compare withVilla Luz). The Movilians use only chemical autotrophy (synthesis of organic molecules from inert minerals).
Here you see a vertical section of the Movile cave (sorry, it is in French but easily understandable: grotte = cave, cloche = bell, lac= lake, niveau de la mer = sea level)
You see a vertical entrance pit made by the people who found the cave and closed by doors isolating the cave from the outside atmosphere. (Movile was initially found by a geologic survey team digging there just by chance). When going down that pit, you first enter an upper level of dry galleries. A second short pit opens on a second set of rooms, filled with water at sea level and forming a sequence of gas filled bells and ponds (see the levels of oxygen, methane, nitrogen and H2s indicated in the figure).
It is where we encounter the Movile life (see the interrupted line indicating the biofilm or bacterial veil floating on the water). At the bottom of this level (see on the left) , deep water is entering the cave through a vertical water filled pit where water rich in H2S is coming from deep down (as I understand, it is a sort of geothermal spring ?).
Look now at the bells. In their water, bacteria oxidize H2S brought in by the geothermal springs and which is thus abundant in both the water and the atmosphere of the bells. Bacteria use this energy to synthesize their organic molecules from the CO2 which is also present in the cave. This is described in the following figure (sorry but right now, it is still in French, question: where does the CO2 come from):
These autotrophic (i.e. rock eating) bacteria serve as food source for other bacteria and fungi organized in filaments and floating in the water. They are heterotroph (they can only eat organic matter and thus they eat lower, autotroph, living beings, i.e. the bacteria). These filamentous bacteria form biofilms (filamentous, slimy veils floating on the surface of the little ponds) and serve as food for small herbivores.
On top of the bacterial veil, terrestrial herbivores (e.g. isopods, collemboles, pseudo-scorpions) live and graze They are themselves eaten by carnivorous species (e.g. spiders, centipedes…). Below the bacterial veil, worms, crustaceans and snails graze also on the bacterial veil and are preys for leeches and other animals. All these animals were trapped half a million years ago and have adapted to their conditions. They display regressive evolution which suppressed their eyes and color pigments. Moreover, they survive without oxygen. Hereafter you see a few of them
A Movile eyeless spider 
A Movile eyeless scorpio
The Movile ecosystem contains 36 terrestrial insect species. Twenty six of them are totally new to science. The density of insects is unbelievable. For instance, more than 1500 collemboles were numbered per square meter of bacterial veil and numerous spiders were observed ( the spiders are known as "Alisco Cristiani"). They have lost their eyes in regressive evolution. This spider species gives us an important clue: his nearest relatives live in the Canary islands. This points toward a specific point: except for bacteria, the Movile fauna seems to originate at a time when
I cannot resist, I have to give you another picture of the eyeless Movile spider, beautiful and frightening, crawling on a gypsum crystal near the bacterial veil:
The aquatic species of Movile are less "out of this worldish". They live in the first ten centimeters under the surface. At this small depth, there is still sufficient oxygen diffusing from the small oxygen content in the air bell. These species had thus to adapt less than the terrestrial ones who were choking in H2S and living in the dark. About 25% of them are new (compare with the terrestrial species where this ratio is about 75%). This suggest that in the past, it was more difficult to crawl in the cave through narrow crevasses than to swim in it through the sumps which, then, linked the cave and the nearby sea or lakes.
According to geologists, the underground network of the Movile bells was created five millions year ago when the black sea emptied itself into the Mediterranean sea. Water and gases from the magma would then have invaded the original cavities and started to carve it more and more. Even today, it exists in the area some sulphurous lakes and swamps with water much like the one of Movile (e.g. lake Kara Oban).
3) Extrapolation: the Bactorg cave
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Hereafter, a rough picture of the cave I envision for my bactorgs to live in. 
An hypogenic cave has been fed for millions of years by water from a deep water rise. It was almost isolated from the surface. At the surface level, another cave was carved by surface waters but was not connected to the hypogenic cave except fror a small unknown connecting flow at a depth of minus 600 meters. When the novel starts, the passage between the hypogenic and the surface cave has just been opened by a minor earthquake. This perturbates the ecosystem of the bactorgs in the hypogenic cave and triggers all the events described in the novel.
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